Spoon blueberry pie filling over hot crust; sprinkle with marshmallows and reserved topping. Return to oven and bake an additional 10 to 12 minutes until marshmallows have melted and are golden brown. Cool on wire rack for 5 minutes.

Carefully lift blondies out using foil overhang; place on serving plate and remove foil. Dust lightly with cinnamon.